Non-instant animation

Hello,

I'm beginner with unity and i'm still more a begginer for animation

My problem is strange, i want change the speed of animation to négative speed for reverse the animation, that works but its not instané.

I record this :

The multiplier speed is correctly change but , i don't understand why this is not instantaneous.


This is the code i use :

Code (CSharp):

1. using System.Collections;
2. using System.Collections.Generic;
3. using UnityEngine;
4.  
5. public class opendoor : MonoBehaviour {
6.     public List<GameObject> electricite;
7.  
8.     public Animator aniopen;
9.  
10.     public bool alimente = false;
11.  
12.     private bool prealim = false;
13.     // Use this for initialization
14.     void Start () {
15.         //aniopen.speed = 0;
16.     }
17.    
18.     // Update is called once per frame
19.     void Update () {
20.         prealim = true;
21.         foreach (GameObject activateur in electricite)
22.         {
23.             if (activateur != null)
24.             {
25.                 elec scriptactivateur = activateur.GetComponent<elec>();
26.                 if (scriptactivateur.electricity == false)
27.                 {
28.                     prealim = false;
29.                  
30.                 }
31.             }
32.         }
33.         if (prealim)
34.         {
35.             alimente = true;
36.             aniopen.SetFloat("mouvementspeed",  1);
37.          
38.  
39.         }
40.         else
41.         {
42.             alimente = false;
43.            
44.             aniopen.SetFloat("mouvementspeed", - 3);
45.  
46.         }
47.         print(alimente);
48.     }
49. }
50.